Compositions for oxidative hair coloring comprise primary intermediates such as p-phenylenediamine and p-aminophenol and couplers such as resorcinol, 3-aminophenol, 5-amino-2-methylphenol and 2,4-diaminophenoxyethanol. However, as noted in U.S. Pat. No. 4,997,451, the use of p-aminophenol (PAP) is being questioned for toxicological reasons.
Because of the toxicological issues, the art has been looking for substitutes for p-aminophenol.
U.S. Pat. No. 4,997,451 describes oxidative hair dyeing compositions based on new 4-aminophenol primary intermediates of the formula 2 which provide oxidative hair dyeing compositions useful for producing red shades. These red shades are comparable in color intensity and brightness to those produced utilizing 4-aminophenol. Moreover, dyes produced through use of the primary intermediates of formula 2 possess a superior toxicological profile. ##STR1##
U.S. Pat. No. 5,047,066 teaches dye compositions for keratinous fibers. The dye compositions contain a 2-substituted 4-aminophenol compound of the general formula 3, 4, 5, and 6, as a developer, and a coupling substance. ##STR2## Compounds 4 and 5 couple with 1-naphthol to produce a vivid reddish hair color. Patentees claim that the new primary intermediates overcome problems of insufficient performance in terms of saturation or vividness of colors, dyeing capability and fastness.
DE 3,441,148 discloses hair dyes containing 4-aminohydroxyalkylphenols of the formula 7 as developers. ##STR3##
U.S. Pat. No. 5,364,413 teaches 3-substituted p-aminophenols of the formula 8, a process for preparing these compounds, their use for dyeing keratinous fibers and the intermediate compounds used in the preparation process. ##STR4##
WO 94/27564 teaches the use of 3-substituted p-aminophenols of the formula 9 for dyeing keratinous fibers and novel 3-substituted p-aminophenols. ##STR5##
DE 3,543,345 discloses oxidative hair dyes based on 4-amino-2-aminomethylphenol of the formula 10. ##STR6##
Although many p-aminophenol derivatives have been patented, only two of them, i.e., 3-methyl-4-aminophenol and 2-aminomethyl-4-aminophenol, are used in commercial hair coloring products. They are primary intermediates. Upon oxidation they couple with conventional couplers to produce an oxidative hair dye. However, these compounds cannot be used as a direct replacement for 4-aminophenol mainly due to color differences. For example, 2-aminomethyl-4-aminophenol couples with 2-methyl-5-aminophenol to color piedmont hair red brown, while a combination of 4-aminophenol and 2-methyl-5-aminophenol colors hair bright orange-red. 3-Methyl-4-aminophenol generally causes a bathochromic shift, as compared to 4-aminophenol.
The object of the invention is to develop a direct replacement for p-aminophenol which, when employed with conventional couplers in oxidative dyeing, gives colors close to that obtained when p-aminophenol is employed with such couplers. This is important because direct replacement allows one skilled in the art to formulate shades based on the existing shades, thereby reducing development time.